how can i fire up contentscript - google-chrome-extension

Question

i got a simple question
i have these3 files
popup.html :
<script>
function buttonClicked(button)
{
chrome.extension.sendRequest({command:button.id});
}
</script>
<input style="width:100%" type="button" value="Click me" id="click" onclick="buttonClicked(this)"/><br/>
background.html :
<script>
function processRequest(request, sender, sendResponse)
{
alert('hi');
sendResponse({});
}
chrome.extension.onRequest.addListener(processRequest);
</script>
and contentscript.js
s = document.getElementsByClassName('st');
if (s[0].innerText != '') {
st = new Array();
for (i = 0;i<s.length;i++) {
st[i] = s[i].innerText;
}
chrome.extension.sendMessage({"message" : st}, function(response) {});
}
i would like to fire up the contentscript each time i click on the button in the popup page be cause somehow the script in the contentscript dosnt work neither or background.html nor on popup.html?
thank you

Answer 1

I've attempted to explain the solution and why to use it in the comments, three times. Since you don't understand it, I'll explain it again with references to your code:
Popup
Move the inline script to an external file, say popup.js.
Delete the inline event listener, and also move it to popup.js.
popup.js
function buttonClicked(button) {
chrome.extension.sendRequest({command: button.id});
}
document.getElementById('click').addEventListener('click', function() {
buttonClicked(this);
});
popup.html
<script src="popup.js"></script>
<input style="width:100%" type="button" value="Click me" id="click"><br>
If you test the previous code, you'll notice that it does not work. That's because the contents of popup.js is executed before the button (which occurs after the <script src> is created. This can be solved in two ways (use either method, but not both):
Recommended: Place <script src="popup.js"></script> before the closing </body> tag in popup.html. Then, you're certain that all elements do exist when the script is executed.
Alternative: Wrap the event listener call in a DOMContentLoaded event:
document.addEventListener('DOMContentLoaded', function() {
document.getElementByUd('click').addEventListener( ... );
});
Background page.
For a more thorough explanation on the available options, see the middle of this answer.
Modify the manifest file, use "background": {"scripts": ["background.js"]}.
Rename background.html to background.js, and remove <script> and </script> from the file.